The present invention relates in general to gas compressors and, more particularly, to devices designed to extract water vapor from the compressed gas, such as by condensing the water vapor contained in the compressed gas by using a cooling effect.
Gas compressor systems, such as air compressors, are widely employed in construction, painting, and mechanical industries and for home use. Compressed gasses, such as air, are used in pneumatic and air handling devices and are stored, such as for use in breathing apparatus.
It is well understood that the relative amount of moisture that a gas is capable of carrying in vapor form varies directly with respect to the temperature of the gas and inversely with respect to the pressure of the gas. Compressing a gas typically raises its temperature; allowing a gas to expand typically lowers its temperature. Gas compressors, such as industrial air compressors, raise the temperature of the air during compression and also raise, of course, the pressure of the air. The rise in the temperature of the air due to compression results in increasing its vapor carrying capacity, typically more than is offset by the effect of the pressure increase (which tends to decrease its vapor carrying capacity). This phenomenon results in substantially all of the original water content of the air remaining suspended in vapor form at the elevated pressure and temperature.
If such moisture laden compressed air is introduced immediately into a downstream pneumatic or air handling or storage device, it will cool toward the ambient temperature and eventually lose its ability to carry such a high water content suspended as vapor. Condensation then will form along all of the components receiving compressed air therefrom.
Many components of devices that operate using or are filled with compressed air are sensitive to water vapor and can be damaged by condensation. To avoid this damage, the water vapor content of the compressed gas must be reduced prior to use.
There are many air-water separation devices commercially available to deal with the problem of water vapor in compressed gas. These devices decrease the water vapor content of compressed gasses before the gas enters the downstream pneumatic or air handling device or components. Air-water separation devices are known by such names as xe2x80x9caftercoolers,xe2x80x9d xe2x80x9cintercoolers,xe2x80x9d xe2x80x9cmist eliminators,xe2x80x9d xe2x80x9cdehumidifiers,xe2x80x9d and xe2x80x9cair dryers.xe2x80x9d
Some vapor elimination devices operate by cooling the compressed air, such as through use of refrigerants, water, or contact with heat conductive metals. Decreases in temperature can be achieved by forcing a high-pressure gas through a constriction, such as a partially opened valve (a xe2x80x9cthrottlexe2x80x9d). This result is known as the Joule-Thomson effect. Other air-water separators use mechanical filters, desiccants, and/or a combination of the above methods. These commercially available drying devices can be integrated into the primary compressor tank, into a secondary cooling tank, or located between the compressor tank(s) and a downstream container or pneumatic device.
One known approach for cooling the compressed air prior to introducing it into the pneumatic system utilizes a length of metal pipe normally with fins or projections to aide in heat dissipation. However, this arrangement may fail to cool the compressed gas sufficiently to provide adequate removal of suspended water vapor and draining off of the condensed water vapor can be problematic.
One example of an aftercooler including a radiator unit can be found in U.S. Pat. No. 6,167,956, which is incorporated by reference as though set forth in full herein. An example of a compressed air dehumidifier can be found in U.S. Pat. No. 6,370,887, which is incorporated by reference as though set forth in full herein. Another known vapor elimination device is an aftercooler manufactured by R. P. Adams Co., Inc. under the trade name ADAMS, which uses water cooling to cool air or gas streams. A known aftercooler using air cooling is manufactured under the trade name ASTROCOOLER(copyright).
A known air dryer is manufactured by Loecy Precision Mfg. and uses a membrane filter to reduce water vapor in the target compressed gases. Another known membrane air dryer, which also includes a silica gel desiccant, is manufactured by Sharpe manufacturing Company and sold under the trade name DRYAIRE(trademark).
Another example of a known desiccant air dryer is manufactured under the trade name ASTURO(trademark). Hankison International, a division of Hansen, Inc., manufactures another known desiccant air drying system. Hankison International also manufactures a combination refrigeration and desiccant drying system, using activated alumina.
Although the known units can be effective, they are often very costly, complex and/or require regular maintenance and replacement of parts. For example, many units utilize consumables, which must be monitored and replaced periodically. Some units contain moveable parts, which tend to wear more than fixed parts and result in shorter useful life for the device. Some known air-water separation devices require an independent source of power.
The cost of air-water separation devices also can be excessive. For example, a unit effective in removing approximately 80% of water vapor in compressed air can cost $300.00 and more, plus the cost of consumables. And, known lower priced air-water separation units are less effective in decreasing water vapor, removing as little as 20%, and many still require use and replacement of consumables. A mechanically simplistic and inexpensive alternative is needed.
The present invention is a low cost, low maintenance integrated vapor extraction device, which uses a combination of Joule-Thomson expansion, e.g., adiabatic expansion of a gas, and a metal or other heat conductive surface to cause a decrease in the temperature of the subject compressed gas, thereby resulting in condensation of water vapor suspended therein onto a surface, which is positioned such that it directs the water condensing thereon into an area of the compressed gas tank where the extracted water can be drained or collected, and a method of use thereof.